The concept of enhancement or improvement of the convection of the electrolyte in electrolytic cells by means of discharges of gas bubbles from an horizontal plane located near the bottom of the cell, in such a way that said discharges improve the productivity and quality electrodeposition of the processes of electrowinning of electrorefining of non ferrous metals, has been known for several decades. In the prior art, there are several designs of devices which claim attaining that objective. One of them, is an isobaric ring installed near the bottom of the cell following its interior perimeter, typically, a rectangular perimeter. These rings or loops are formed by interconnected profiles or tubes of square, rectangular or circular cross section, to form rectangular structural frames that carry in their interior the gas necessary to generate bubbles emerging from the inferior portion of the cell, under the electrodes, and rising upwards to the surface of the electrolyte. For that purpose, such rings are crossed from side to side by diffuser ducts or perforated hoses, whereby the bubbles actually emerge from perforations in the diffusers or hoses, having an initial diameter determined by the diameter of the perforations and by the height of the electrolyte hydraulic column; the bubble diameters increase as the bubbles rise, due to the diminishing hydraulic pressure towards the surface of the electrolyte. Several patent documents disclose a solution to achieve such electrolyte agitation in an electrodeposition cell.
Document U.S. Pat. No. 1,260,830, published Mar. 26, 1918, titled “Electrolytic deposition of copper from acid solutions” discloses copper electrodeposition by means of continuous agitation of the electrolyte, particularly sweeping the surface of the vertical anodes with bubbles of a mixture of sulfur dioxide gas and vapor, projected from orifices perforated in transversal lead pipes, disposed parallel to, and under, the anodes in the cell, with the orifices oriented in such a manner that the fluid emerges in an oblique angle striking the surface of the anodes, forcing a continuous electrolyte circulation, with maximum agitation and turbulence occurring by the impact of the mixture directly on the faces of the anodes.
Document U.S. Pat. No. 3,928,152, published Dec. 23, 1975, titled “Method for the electrolytic recovery of metal employing improved electrolyte convection”, describes a method of high quality copper electrodeposition on permanent cathodes plates at very high current densities. To achieve high productivity, the separation between electrodes is reduced to a minimum with separators—distances that position them exactly relative to each other, and simultaneously, provide very aggressive continuous agitation of the electrolyte by gas sparging tubes placed under each cathode, disposed to sweep the faces of the cathodes with curtains of bubbles that emerge from holes perforated in the tubes.
Document U.S. Pat. No. 3,959,112 published May 25, 1976, under the title “Device for providing uniform air distribution in air-agitated electrowinning cells”, discloses air bubbling device, placed transversely to the cell length and parallel on both faces of the cathodes, just below their lower edge. The devices comprise rigid perforated tubes that allow discharging air in bubbles of relatively large diameter with minimum pressure loss, whereby said tubes are enclosed externally with sleeves of larger diameter permeable material which oppose resistance and restrict the passage of the air bubbles, forcing them to emerge continuously from the sleeves as curtains of very fine bubbles that then sweep vertically both faces of the cathode and thus inhibit the formation of rugosities in the metal deposition on the cathode surface.
U.S. Pat. No. 4,263,120, published Apr. 21, 1981, under the title “Electrolytic cell for the recovery of non ferrous metals and an improved anode therefor”, discloses the operation of the electrolytic process with electrolyte agitation by using of perforated gas bubbler tubes placed parallel under the anodes to create ascending electrolyte turbulence in the interfaces of the electrodes.
Document CL 527-01, published Sep. 27, 2002, today patent CL 44.803 titled “System and method to capture and extract acid mist from polymer concrete containers, were the side, frontal and back walls are modified to allow horizontal seat of a thermal cover that forms a chamber connected to extraction ducts, method of fabrication and container for such purpose”, discloses a stratified polymer concrete container for electrolytic cell, together with several means to eliminate acid mist, to increase productivity and thermal performance with high current density in the processes of electrowinning and electrorefining of non ferrous metals, specially copper, which includes, among other elements, a duct for injection of fresh external air with gas diffusers installed parallel, and in a horizontal plane, in the lower portion of the cell, that direct air bubbles rising from under the electrodes.
Document CL 2120-2004, published Jul. 28, 2006, (equivalent to document WO 2005/019502) titled “Method to operate and electrolytic cell . . . ” discloses gas diffusers for the transfer by gas bubbling to liquid means comprising an element consisting of a body of cylindrical connection that is prolonged in a tube conical zone ending in a closed end; between the cylindrical zone and the end zone there is a multi perforated separation wall trough which from the interior of the cylindrical body air circulates at constant pressure and velocity, generating a gas stream that distributes forming gas minijets.
Document CL 727-2006, published Jul. 7, 2006, titled “Electrolyte agitating device that consist of a reticulated structure, flat and of regular plant, formed of non electric conducting polymer composite materials resistant to corrosion, and, comprising an isobaric gas distribution ring, gas diffuser means; and electrolyte agitation system”, discloses an electrolyte agitation apparatus immersed in containers for electrolytic cells used in the processes of electrowinning and electrorefining of non ferrous metal, formed by pipes of anticorrosive and non conducting materials, joined together by connecting elements, were said joined pipes cross over from one side to the other by gas diffuser means, where said joined pipes and connected elements form an isobaric ring, which is encapsulated in the interior of a continuous profile, formed monolithically of an anticorrosive dielectric polymer composite material, forming one flat, perimetral parallelepiped structure, homologous to the shape of the bottom of the container, where said perimetral structure is reticulated to impart rigidity and necessary structural resistance to be self supporting.
In general, prior art, isobaric rings are formed, by tubes of different thermoplastic materials, especially PVC, since the ring constituent materials must not be electrically conducting, resistant to heat and resistant to electrolyte corrosion present in the cell. Likewise, tubes exist that are within some type structural material to protect them from heat, from the electrolyte, as well as to provide some resistance to mechanical stresses.